Process Management

Managing applications states

PM2 is a process manager. It manages your applications states, so you can start, stop, restart and delete processes.

Start a process:

$ pm2 start app.js --name "my-api"
$ pm2 start web.js --name "web-interface"

Now let’s say you need to stop the web-interface:

$ pm2 stop web-interface

As you can see the process hasn’t disappeared. It’s still there but in stopped status.

To restart it just do:

$ pm2 restart web-interface

NB: starting PM2 2.1.x, restarts are immutable, meaning that environnement changes will not change your process, see –update-env

Now you want to delete the app from the PM2 process list. You just have to enter the following commands:

$ pm2 delete web-interface

Since PM2 2.4.0, you can also restart/delete/stop/reload applications via regex (this one will only restart http-1 and http-2 but not http-3):

$ pm2 restart /http-[1,2]/

Note : Regex are defined by leading and ending ‘/’ and they are tested against applications name only (not the process id).

You can declare options via configuration file too.

Process listing

To list all running processes:

$ pm2 list
# Or
$ pm2 [list|ls|l|status]

To get more details about a specific process:

$ pm2 show 0

Start any process type

For scripts in other languages:

$ pm2 start echo.pl --interpreter=perl

$ pm2 start echo.coffee
$ pm2 start echo.php
$ pm2 start echo.py
$ pm2 start echo.sh
$ pm2 start echo.rb

The interpreter is set by default with this equivalence:

{
  ".sh": "bash",
  ".py": "python",
  ".rb": "ruby",
  ".coffee" : "coffee",
  ".php": "php",
  ".pl" : "perl",
  ".js" : "node"
}

Binary code execution

$ pm2 start ./binary-app

Process configuration

To run a non-JS interpreter you must set exec_mode to fork_mode and exec_interpreter to your interpreter of choice. For example:

{
  "apps" : [{
    "name"       : "bash-worker",
    "script"     : "./a-bash-script",
    "exec_interpreter": "bash",
    "exec_mode"  : "fork_mode"
  }, {
    "name"       : "ruby-worker",
    "script"     : "./some-ruby-script",
    "exec_interpreter": "ruby",
    "exec_mode"  : "fork_mode"
  }]
}

Max Memory Restart

PM2 allows to restart an application based on a memory limit.

Note that the max memory restart options are graceful (if your application supports graceful actions of course).

CLI

$ pm2 start big-array.js --max-memory-restart 20M

JSON

{
  "name"   : "max_mem",
  "script" : "big-array.js",
  "max_memory_restart" : "20M"
}

Programmatic

pm2.start({
  name               : "max_mem",
  script             : "big-array.js",
  max_memory_restart : "20M"
}, function(err, proc) {
  // Processing
});

Units

Units can be K(ilobyte), M(egabyte), G(igabyte).

50M
50K
1G